The present invention relates to a transmission shaft and bit mounting arrangement of a motor-driven hand drill which uses a magnet to attract the bit, and a stop member controlled to stop the bit from axial movement.
FIG. 1 shows the bit mounting arrangement of a motor-driven hand drill according to the prior art. According to this arrangement, a bit A is mounted in a coupling hole C1 on a chuck C, and a tool D is used to fix the bit A and the chuck C together, enabling the bit A to be turned with the chuck C by a motor drive B. This arrangement has drawbacks. During the operation of the motor-driven hand drill, the bit A tends to be forced out of the coupling hole C1 of the chuck C by the vibration of the motor drive B. Further, the procedure of replacing the bit A is complicated because the tool D must be used.